/*
 * Copyright 1999-2012 Alibaba Group.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
/**
 * (created at 2011-1-19)
 */
package fm.liu.timo.parser.ast.expression.primary;

import java.util.ArrayList;
import java.util.List;
import fm.liu.timo.parser.ast.expression.Expression;
import fm.liu.timo.parser.util.Pair;
import fm.liu.timo.parser.visitor.Visitor;

/**
 * <code>'CASE' value? ('WHEN' condition 'THEN' result)+ ('ELSE' result)? 'END' </code>
 * 
 * @author <a href="mailto:shuo.qius@alibaba-inc.com">QIU Shuo</a>
 */
public class CaseWhenOperatorExpression extends PrimaryExpression {
    private final Expression                         comparee;
    private final List<Pair<Expression, Expression>> whenList;
    private final Expression                         elseResult;

    /**
     * @param whenList never null or empry; no pair contains null key or value
     * @param comparee null for format of <code>CASE WHEN ...</code>, otherwise,
     *        <code>CASE comparee WHEN ...</code>
     */
    public CaseWhenOperatorExpression(Expression comparee,
            List<Pair<Expression, Expression>> whenList, Expression elseResult) {
        super();
        this.comparee = comparee;
        if (whenList instanceof ArrayList) {
            this.whenList = whenList;
        } else {
            this.whenList = new ArrayList<Pair<Expression, Expression>>(whenList);
        }
        this.elseResult = elseResult;
    }

    public Expression getComparee() {
        return comparee;
    }

    /**
     * @return never null or empty; no pair contains null key or value
     */
    public List<Pair<Expression, Expression>> getWhenList() {
        return whenList;
    }

    public Expression getElseResult() {
        return elseResult;
    }

    @Override
    public void accept(Visitor visitor) {
        visitor.visit(this);
    }
}
